This proposal has four major objectives: 1. Development of a center for the housing and study of hereditary porphyria in bovine and other non-human species, with special emphasis on a search for models of hereditary hepatic porphyria; 2. Biochemical studies of porphyrin and heme metabolism, including application of marrow culture techniques to the study of enzymes of heme biosynthesis in clones of similarly maturing cells, and assays of renal erythropoietin production in clones of similarly maturing cells, and assays of renal erythropoietin production & hemoprotein content in hamsters with renal porphyria; 3. Continued investigation of the potential use of porphyrins for tumor therapy; and 4. Development and application of new techniques for use in these areas.